java 使用反射和策略模式 优化多个if else
说明 ： 以汽车品牌为例，比如大众汽车，和本田汽车， 车都有各自的颜色及价格 ，以此为背景，进行代码实例演示
包结构
代码演示
汽车类型枚举
package com.cn.java.base.common.enums;
/**
* @author hg
* @desc 1.0
* @date 2020/5/31 16:18
*/
public enum CarTypeEnum {
HONDA_CAR(1, "本田"),
VW(2, "大众"),
UNDEFINE(-1, "未定义异常信息");
private int code;
private String msg;
CarTypeEnum(int code, String msg) {
this.code = code;
this.msg = msg;
}
public static String msg(int code) {
for (CarTypeEnum m : CarTypeEnum.values()) {
if (m.getCode() == code) {
return m.getMsg();
}
}
return UNDEFINE.getMsg();
}
public int getCode() {
return code;
}
public void setCode(int code) {
this.code = code;
}
public String getMsg() {
return msg;
}
public void setMsg(String msg) {
this.msg = msg;
}
}
自定义注解，绑定策略实现类
package com.cn.java.base.common.annotation;
/**
* @author hg
* @desc 1.0
* @date 2020/5/31 15:33
*/
import com.cn.java.base.common.enums.CarTypeEnum;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
public @interface StrategyType {
//策略名
CarTypeEnum carType();
}
step1: 首先定义通用策略接口 CarBaseStrategy
package com.cn.java.base.strategy;
/**
* @author hg
* @desc 1.0
* @date 2020/5/31 16:04
*/
public interface CarBaseStrategy {
/**
* 汽车颜色
* @return
*/
String carColor();
/**
* 汽车价格
* @return
*/
String carPrice();
}
step2: 定义各个汽车实现
本田汽车实现
package com.cn.java.base.strategy.car;
import com.cn.java.base.common.annotation.StrategyType;
import com.cn.java.base.common.enums.CarTypeEnum;
import com.cn.java.base.strategy.CarBaseStrategy;
import org.springframework.stereotype.Component;
/**
* @author hg
* @desc 1.0 本田汽车
* @date 2020/5/31 16:10
*/
@Component
@StrategyType(carType = CarTypeEnum.HONDA_CAR)
public class HondaCar implements CarBaseStrategy {
@Override
public String carColor() {
return "本田铂金灰";
}
@Override
public String carPrice() {
return "价格 - 15W";
}
}
大众汽车实现
package com.cn.java.base.strategy.car;
import com.cn.java.base.common.annotation.StrategyType;
import com.cn.java.base.common.enums.CarTypeEnum;
import com.cn.java.base.strategy.CarBaseStrategy;
import org.springframework.stereotype.Component;
/**
* @author hg
* @desc 1.0 大众汽车
* @date 2020/5/31 16:09
*/
@Component
@StrategyType(carType = CarTypeEnum.VW)
public class VwCar implements CarBaseStrategy {
@Override
public String carColor() {
return "大众铂金灰";
}
@Override
public String carPrice() {
return "价格 - 15W";
}
}
step3: 定义策略实例缓存容器
package com.cn.java.base.strategy;
import java.util.HashMap;
import java.util.Map;
/**
* @author hg
* @desc 1.0
* @date 2020/5/31 16:05
*/
public class CacheCollection {
private static Map ALL_DATA_SOURCE;
static {
ALL_DATA_SOURCE = new HashMap<>(100);
}
/**
* 根据策略名获取 Class
* @param dsType
* @return
*/
public static Class getDS(String dsType) {
return ALL_DATA_SOURCE.get(dsType);
}
/**
* 策略名为 key,Class 为 value
*/
public static void putClass(String dsType,Class clazz){
ALL_DATA_SOURCE.put(dsType,clazz);
}
}
step4: springboot启动 初始化策略实例，并加载至容器中
package com.cn.java.base.strategy;
import com.cn.java.base.common.annotation.StrategyType;
import org.springframework.stereotype.Component;
import javax.annotation.PostConstruct;
import java.io.File;
import java.net.URL;
/**
* @author hg
* @desc 1.0
* @date 2020/5/31 16:05
*/
@Component
public class InitDataSource {
private String packageVo="com.cn.java.base.strategy.car";
@PostConstruct
public void init() {
initAllDataSourceType(packageVo);
}
private void initAllDataSourceType(String packageVo) {
URL url = this.getClass().getClassLoader().getResource(packageVo.replace(".", "/"));
File dir = new File(url.getFile());
for (File file : dir.listFiles()) {
if (file.isDirectory()) {
continue;
} else {
String className = packageVo + "." + file.getName().replace(".class", "");
try {
Class clazz = Class.forName(className);// class cn.haoxy.ref.inter.impl.faceRecognition
//判断这个类上是否存在指定的注解
if (clazz.isAnnotationPresent(StrategyType.class)) {
//如果存在,得到此注解的value值
StrategyType dataSourceType = clazz.getAnnotation(StrategyType.class);
//放入容器 此位置使用枚举类型约定策略类型
CacheCollection.putClass(dataSourceType.carType().name(), clazz);
}
} catch (ClassNotFoundException e) {
e.printStackTrace();
continue;
}
}
}
}
}
step5: 定义策略调度器
package com.cn.java.base.strategy;
import org.springframework.beans.BeansException;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationContextAware;
import org.springframework.stereotype.Component;
/**
* @author hg
* @desc 1.0
* @date 2020/5/31 16:07
*/
@Component
public class StrategyManager implements ApplicationContextAware {
private ApplicationContext applicationContext;
public CarBaseStrategy getStrategyInstance(String dsType) {
Class clazz = CacheCollection.getDS(dsType);
CarBaseStrategy crBaseStrategy = (CarBaseStrategy) applicationContext.getBean(clazz);
return crBaseStrategy;
}
@Override
public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
this.applicationContext = applicationContext;
}
}
step6: 调度策略
package com.cn.java.base.controller;
import com.cn.java.base.common.enums.CarTypeEnum;
import com.cn.java.base.common.utils.R;
import com.cn.java.base.strategy.CarBaseStrategy;
import com.cn.java.base.strategy.StrategyManager;
import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
/**
* @author hg
* @desc 1.0
* @date 2020/5/31 16:34
*/
@Slf4j
@RestController
@RequestMapping("strategy")
public class StrategyController {
@Autowired
private StrategyManager strategyManager;
@RequestMapping("strategyTest")
public R strategyTest(){
CarBaseStrategy car = strategyManager.getStrategyInstance(CarTypeEnum.HONDA_CAR.name());
System.out.println(car.carColor());
System.out.println(car.carPrice());
return R.ok().put("data","success");
}
}
输出结果
